How to create a method at runtime using Reflection.emit

I'm creating an object at runtime using reflection emit. I successfully created the fields, properties and get set methods. Now I want to add a method. For the sake of simplicity let's say the method just returns a random number. How do I define the method body?

EDIT:

Yes, I've been looking at the msdn documentation along with other references and I'm starting to get my head wrapped around this stuff. I see how the example above is adding and/or multplying, but what if my method is doing other stuff. How do I define that "stuff" Suppose I was generating the class below dynamically, how would I create the body of GetDetails() method?

class TestClass
{
    public string Name  { get; set; }
    public int Size  { get; set; }

    public TestClass()
    {
    }

    public TestClass(string Name, int Size)
    {
        this.Name = Name;
        this.Size = Size;
    }

    public string GetDetails()
    {
        string Details = "Name = " + this.Name + ", Size = " + this.Size.ToString();
        return Details;
    }
}